The present disclosure generally relates to communication devices and methods and, more particularly, to the full duplex communication device with the energy saving mode and the communication method thereof.
Nowadays, many electronic devices adopt the energy saving mechanism for utilizing the power more wisely, extending the battery usage time of the portable devices, and therefore achieving better environmental protection. For example, the Energy Efficient Ethernet (EEE) standard, developed by the IEEE 802.3az task force, defines several mechanisms for reducing the power consumption. During the periods of low data activity, the EEE-compatible transceivers may enter the power saving mode (a.k.a., the quiet mode, the sleep mode, the energy saving mode, etc.) and stop sending idle signals. The energy for sending idle signals in the power saving mode may therefore be saved.
In the High-Definition Multimedia Interface (HDMI), the fast Ethernet technology, i.e., 100BASE-TX of the IEEE 802.3u standard, is used in the HDMI Ethernet Channel (HEC) communication. Conventional 100BASE-TX transceivers may be modified to be compatible with the EEE standard with some changes. The HEC transceivers, although using the similar technology with 100 BASE-TX transceivers, may not be compatible with the EEE standard for several reasons.
For example, although both the 100BASE-TX transceivers and the HEC transceivers may operate in the full duplex mode, the 100BASE-TX transceiver trans-mits signals on one twisted pair of conductors and receives signals on another twisted pair of conductors. On the other hand, the HEC transceiver may transmit and receive signals on the same twisted pair of conductors simultaneously. When the near-end HEC transceiver receives the signals transmitted from the far-end HEC transceiver, the near-end HEC transceiver therefore may also receive the signals transmitted by itself. When the near-end HEC transceiver and the far-end HEC transceiver transmit the same signals, both HEC transceivers may not differentiate the near-end signals and the far-end signals and therefore fail to function correctly.
Besides, in the idle mode or in the connection establishment process, the HEC transceivers on both ends need to transmit idle signals. The HEC transceivers continuously and repeatedly transmit the pseudo random code of several thousand bits as the idle signals. The HDMI standard does not adopt the master-slave mechanism and does not require the near-end and the far-end HEC transceivers to use different scramblers. Thus, in the idle mode or in the connection establishment process, the near-end and the far-end HEC transceivers may transmit the same idle signals and therefore fail to function correctly.
Moreover, although the HEC transceivers shall transmit the signals with a 125 MHz frequency, there still may be a difference existed between the transmission frequencies of the transceivers on both ends. For example, a difference with ±200 ppm of the transmission frequency is tolerable in some technical standards. Therefore, even if the near-end and the far-end HEC transceivers are configured to transmit the idle signals from different positions of the same pseudo random code, the difference between the transmission frequencies may still cause the near-end and the far-end HEC transceivers to transmit the same idle signals after a period of time. The HEC transceivers may still fail to function correctly in this configuration.
Furthermore, if the HEC transceivers are to support the EEE function, the HEC transceivers shall avoid transmitting the same idle signals after leaving the power saving mode, which may cause the malfunction of the HEC transceivers.